Refrigerating system



M. P. FRERES REFRIGERATING SYSTEMS Filed April 30, 1940 2 Sheets-SheetDec. 29', 1942 1 w 3 y /s m i i 7 a W 9 w W x V, 6 7 W r m u W 5./

Dec. 29, 1942. P FRERES 2306534 REFRIGERATING SYSTEMS Filed April 30,1940 2 Sheets-Sheet '2 .Fig. 3

NVENTOR Patented Dec. 29,1942 I 2,306,534

UNITED STAT'ES PATENT OFFICE I, REFBIGE SYSTEM i Max P. F'ercs, Chicago,Ill., assino* to Anthony F. Hoesel, Chicago, Iii. 4

Application April 30, 1940, Serial No. 332589 2 Claims. (Ci. 62-8) A Thepresent invention relates to the preserva- Under the` above conditionthe refrigeratln tion o! foodstufls by means or refrigeration, andsystem would operate 45 minutes' out of each hour especially hydrousfood such as meat, etc. and set up a rather vigorous convection circula-V In the refrigeration art it is well known that tion of cooled anddehydrated air within the meats may be kept, in the unfrozen state, forat 5 walk-in cooler. e

least limited periods, with adequate refrigeration The term "dehydrated"is here used only in its plus proper air circulation. What is not sogenrelative sense as meaning air oi only slightly erally known, however,is that for the proper lower dew point than the air immediatelysurpreservation of meats a -certain constant minirounding the surfacesof the meat, which is conmum dehydration must take place; otherwise them tinuously surrendering moisture to such air. surfaces of meat tend tobecome slimy and pre- Now many of these retail meat markets are sent anunsalable appearance, as well as increasunheated, or at least onlypartially heated during ing the amount of bacteria thereon. the wintermonths, in which the temperature of A retail meat market generally has alarge the air, outside the walk-in cooler, may drop to walk-in cooler,where bulk meats are kept and l 50 F., or even less.

from which the display cases are replenished Under such Winterconditions we find that the upon demand. temperture difl'erence nowbecomes 50 F., minus These walk-in coolers are generally constructed 34F., equals 16 F., and the hourly heat load of insulated walls having aheat transfer of apper square foot of walk-in cooler wall surfaceproximately '.1 B. t. u. per hour per square foot 20 becomes .125 B. t.u. times 16 F., equals 2 B. t. u. per degree Fahrenheit temperaturediii'erence be- Since the refrigerating system has a capacity of tweeninside and outside temperatures. This is 8.3 B. t. u. per square footper hour, we now find termed the wall heat inleakage. The total heatthat instead of Operating 75 per cent of the time, load of such awalk-in cooler is the sum of the as in the summer condition, it onlyoperates wall heat inleakage, plus the service load in open- 2+8.3equals 24 per cent of the time, or 60 times ing the doors, plus theproduct load. .24 equals 14.4 minutes out of the hour.

` For the present purpose, we may disregard the During the 45.6 minutesthat the refrigeration product load since once the product is cooledsystem is inoperative, we find that the air, inside down there is nofurther product load. the walk-in cooler, tends to become stagnated andIn general, the service load equals about 25 allow the relativehumidity'of the air surrounding per cent of the wall heat inleakage;therefore; the meat surfaces to sufllciently increase so that for ourpurposes, we shall consider the heat the moisture migrating from insidethemeat tends i load as being .125 B. t. u. per hour per square tocollect upon the surface thereoi and make the foot per degree Fahrenheittemperature difference same slimy. between the inside and outside of thecooled In the past there have'been several attempts space. `made toreduce the amount of off-time of the Since a refrigerating system musthave aderefrigeration system during the Winter months, quate capacity totake care of the maximum heat and one of them consisted of placingheating load and further since thesesystems are-genmeans within thewalk-in cooler. This operates erally intermittently operated on thebasis of 40 successfully, although it entails a greater conapproximatelynot over 75 per cent of the total sumption of energy and therefore iswasteiul. time, we find that the refrigerating capacity, per v Anothermeans on installations having multiple' square foot, would then becomputed as .166 cooling units in the walk-in cooler, is to close B. t.u. per hour per degree Fahrenheit, down one or more of the coolingunits, but this such walk-in coolers are generally operated at can beemployed only on such multiple cooling 34 degrees Fahrenheit, which witha summer conunit installations, and is not applicable to single ditionof outside temperature of, say, 84 degrees cooling unit installations.Furthermore, each Fahrenheit, gives a temperature difierence of coolingunit generally serves to maintain its propdegrees Fahrenheit between theinside and outer air circulation within a restricted portion of the Vside of the walk-in cooler. 50 walk-in cooler, and in many instances theslim- In order to properly refrigerate such a walking is aggravated atsuch portions having thein cooler, as above, the refrigerating capacitycooling unit closed down. would have to be .166 B. t. u. times 50 F.,equals With cooling units, of the forced air circulation 8.3 B. t. u.,per hour per square foot of walk-in type', we fnd applications whereinthe forced air cooler wall surfaces. ,35 circulation during the Wintermonths is decreased during the operation of the refrigeration system,resulting in a more dehydrated air being circulated; and is thenincreased during the ofitime cycle, resulting in a more rapiddefrosting' of the cooling unit surfaces and a consequent rapidrejection of such defrosted moisture to the sewer.

The present invention contemplates Operating a cooling unit, during thesummer months, exactly as in the present conventional manner: namely,utilizing the entire amount of heat transfer surface comprising suchcooling unit. The on-time cycle would then be 45 minutes, and theoff-time cycle would be minutes, for the given conditions.

During the Winter time I intend to reduce the effective heat transfersurfaces, of the cooling unit, sufliciently, in the manners subsequentlydescribed, so that the cooling action is sufliciently modified, frompresent conventional practice, that sliming of meats is obviated.

An object of the present invention is to prevent sliming of meats, etc.,during conditions of low outside temperature surrounding the Compartmentin which such meats, etc., are kept.

:A further object of the present invention is to provide an improvedrefrigeration system to accomplish the aforementioned object.

In the drawings:

Figure 1 is an elevational'diagrammatic view of a, refrigerating system,in part, and embodying the invention.

Figure 2 is a cross-sectional view of a pressure difl'erential valveused in the embodiment of the invention shown in Figure 1.

Figure 3 is an elevational diagrammatic view of a refrigeration system,in part, showing a modified fonn of the invention.

Referring to the drawings:

In Figure 1, a compartment 4 is being cooled by the cooling unit 5,having an inlet 6 and an outlet 1. connected to the inlet 6 is apressure difierential valve 8 to the inlet of which is connected athermostatically controlled expansion valve 9, so well known in therefrigerating art that it will sufflce to here state that its operationis subject to two forces, one being a force proportlonal to thesuperheat of the refrigerant vapor leaving the cooling unit and tendingto open the refrigerant feed, through said valve, with increasingsuperheat and vice versa; the other being a force proportional to the'expanded refrigerant pressure within said valve and tending to close therefrigerant feed with increasing refrigerant pressure and vice versa.

and consequent force of which may be varied by adjustment of thethreaded combination valve guide and spring abutment 20.

Assume the system in operation, during the summer period, we now adjustthe spring abutment so that the spring I& is practically free, at whichtime the compresion spring 2! lifts the check valve !8 into full openposition and there is then an unrestricted flow passage through thepassage ll. The thermostatically controlled expansion valve 9 is nowunder the direct influence of the refrigerant pressure, within thecooling unit 5, tending to close the feed through the valve 9 withincreasing refrigerant pressure. It is further under the influence ofthe refrigerant vapor temperature, in the suction conduit l2, tending toopen the feed, through the valve 9, with increasing temperature.

Assuming that the temperature of the refrigerant liquid, within thecooling unit 5, is 15 F., and that the valve 9 is adjusted to feedrefrigerant fluid at such rate as to maintain a. 10 F. superheat, wewould find that the temperature of the suction conduit IZ, adjacent thetemperature feeler bulb Il, is now 15 F. plus 10 F., equals F. Underthis condition (10 F. superheat) the cooling unit 5 is Operating atpractically its maximum capacity without having unvaporized refrigerantliquid passing into the suction conduit l2 and to the compressor withall the deleterious effects consequent thereto.

` acquired in the following manner:

From the valve 9, a capillary tube i E leads to a temperature feelerbulb II, which comprises, in part, a thermostatically responsive systemaffecting the refrigerant feed, through valve e, proportional to thetemperature of the refrigerant vapor passing through the suction conduit!2, which connects to the outlet 1, of the cooling unit 5.

A refrigerant liquid conduit !3 connects to the inlet of the valve 9. Arefrigerant compressorcondenser system, not shown, serves to evacuatethe refrigerant vapor from the suction conduit I2, compress and condensethe same, which is then led, under high pressure and in liquid form, tothe refrigerant liquid conduit l3.

In Figure 2, the differential pressure valve B comprlses a casing |4having an inlet l5 and outlet IS between which is interposed a valvepassage I'I having a check valve IB, which is constantly urged intoclosing position, as shown, by

means `of the compression spring !9, the length In order for the coolingunit 5 to absorb heat from the compartment 4, it must be at a lowertemperature than the temperature of the compartment 4. Now, if we adjustthe valve 9 to maintain a 10F. superheat, the valve 9 will feed justsufilcient refrigerant liquid so that something less than of thesurfaces of the cooling' unit 5 will produce effective refrigeration,due to vaporization of refrigerant liquid. The remaining percentage ofsuch surface, tending to absorb heat from the compartment 4, then addsheat to the refrigerant vapor. This additional heat is the superheat.The greater the amount of superheat, naturallyfthe greater the amount ofsurface necessary for the additional heat, and consequently the lesseramount of surface available for effective refrigeration. The converse isalso true.

Now as the temperature outside of the compartment 4 decreases, we findthat the potential capacity of the cooling unit 5 is relatively toogreat, which results in too great an off-time period of therefrigerating system, producing sliming of meats, etc.

We now adjust the spring abutment 20 so that the compression spring ISforces the check valve 13, with some considerable force, to close thepassage H. The check valve |8 now tends to maintain a pressuredifference between the inlet !5 and outlet !6. Since the expansion valve9 connects to the inlet !5 it will be noted that its previous closingforce, namely the pressure within the cooling unit 5, is now augmentedby the differential pressure necessary to open the check valve !8against the pressure of the spring I 9. In order for the valve 9 to feedrefrigerant liquid to the cooling unit 5, it now becomes necessary iorthe opening force, superheat, to be additionally augmented. Therefore wenow find that less of the surface of the cooling unit 5 is produclngeffective refrigeration, in order that more of such surface can providethe additional superheat.

In effect, the result is just the same as if we had replaced the coolingunit with one of lesser physical dimensions or heat transfer capacity.

While I have shown no means for intermittently Operating therefrige'ation system, there are just two means, both universallyemployed and well known in the art. In the first method of control wemay employ a room temperature thermostat, which will start the systemupon some high compartment temperature and stop the system upon some lowcompartment temperature. Inthis instance the temperature of theeffective surfaces of the cooling unit 5 during the on-time cycle, wouldbecome lower, during Winter time operation, at which time less of thecooling unit surface would be effective, than the temperature of theincreased effective surfaces during the summer time' operation.

While the operation, with room thermostat control, would tend to have acomparatively long off-time cycle, which was previously mentioned ashaving an ill effect, we would find that the reduced temperature, of theefiective surfaces of the cooling unit 5, Would result in a greaterdehumidifying effect upon the circulated air during the on-time cycle.In consequence, the ill effects of long off-time cycle are practicallycanceled by the greater dehumidifying efl'ect of lower temperatureon-time cycle.

In the second method of control, which is more generally employed, weutilize a pressurestat. which starts and stops the system responsive tosome certain high pressure and some certain low pressure respectively ofthe refrigerant within the cooling unit 5.

Since volatile refrigerants have a definite pressure-temperaturerelationship, such pressurestat control method resolves itself intostarting and stopping the system at some definite high temperature anddefinite low temperature respectively of the cooling unit 5. Thetemperature of the cooled compartment 4, then tends to float with thetemperature of the cooling unit 5.

Assuming such pressurestat control set to start the system at, say 33 F.temperature, and stop the same at, say F., we would find, during summertime operation, that the on-time cycle would be comparatively long. Nowwhenever we adjust the pressure differential valve 8 for Winter timeoperation, we eifectively use less of the cooling unit 5., Therefore,the traverse from 33 F. to 15 F. is accomplished in a much shorterperiod of time than the time period .if we utilized th'e potentialmaximum capacity of the cooling i unit 5.

Whereas utilizing the cooling unit surfaces to their maximum mightresult in Operating cycles of 15 minutes on-time with 45 minutesoff-time, we now find that restricting the effective coolingunitsurfaces results in Operating cycles of possibly 5 minutes on-timewith' 15 minutes off-time.

In Figura 3 I show a modified form of the invention, wherein acompartment 30 is cooled by means of a cooling unit 3I having an inlet32 and outlet 33. The thermostatically controlled expansion valves 34and 35 have their outlets,`

36 and 31, respectively, connected to said inlet 32. The refrigerantliquid conduit 38 connects to the valve inlets 39 and 40 by means of theconduits 4l and 42 respectively. Interposed between the refrigerantliquid conduit 38 and the conduit 42 is a hand operated shut-off valve43.

Depending from the thermostatically controlled expansion valve 34 is acapillary tube 44 in communication with the temperature feeler bulb 45,adjacent the outlet 33, which forms, in part, the thermostatic controltending to maintain, by means of controlling the rate of refrigerant'liquid feed through the valve 34, a 10 F. superheat of the refrigerantvapor passing through the outlet 33. The valve 34 is adjusted tomaintain this 10 F. superheat.

Deper'ding from the thermostatically controlled expansion valve 35 is acapillary tube 46 in communication with the temperature feeler the valve34, tends to make practically the entire surfaces, of the cooling unit3l, effective in tr'ansferring heat to the refrigerant liquid so fed.

Since the temperature feeler bulb tends to control the feed through thevalve 34 so as to maintain a 10 F. superheat, at the outlet 33, thevalve '35 cannot feed refrigerant liquid, since it is adjusted tomaintain a much higher degree of superheat. Under this condition ofoperation the valve 35 is closed at all times; r

During the Winter time the shut-off valve 43 is closed and norefrigerant liquid can therefore feed through the valve 34. In this casethe refrigerant liquid feeds through the valve 35 responsive to thetemperature of the temperature feeler bulb 41, which, tending to controlthe feed through the valve 35 so as to maintain a greater than 10 F.superheat, then tends to make only part of the surfaces, of the coolingunit 3l, effective in transferring`heat to refrigerant liquid.

.The increased amount of surface, which might relatively be termedineffective, serves to accumulate the additiona superheat added to therefrigerant vapor.

The above numerical value of 10 F. superheat is merely used as a basisof comparison, since that is a rather common point of adjustment in theart. It may range from a lesser degree to even a higher degree incertain instances.

From 'the above it will be noted that I have provided several manners ofregulating a refrigerating system, all based upon varying cooling unitcapacity by means of Operating the same with various degrees ofsuperheat of the refrigerant vapor leaving such cooling unit.

By this means, I am enabled to so modify the Operating characterstics,of a refrigerating system, as to prevent the sliming of meats, etc.,during the Wintera time, while yet having adequate refrigeratingcapacity for the summer time heat load.

While the above are specific concepts of the invention, many variations,,in detail, may be employed without dep'arting from the spirit and oneindividual to each valve, and responsive to temperature conditions atthe outlet of the cooling unit, one of said valves being adjusted tomaintain a. low degree of superheat, the other of said val'ves beingadjusted to maintain a high degree of superheat, and means to close oi!the fluid flow through the valve adjusted to maintain the low degree ofsuperheat thereby establishing flow through the other of said valves.

2. The combination with a compartnent of an intermittently operatedretrigerating system for cooling the same; said system comp'ising a.cooling unit having an inlet and an outlet between which a. volatile'rerigerant is circulated; an expansion valve connected to said inletand controlling the rate oi' ref-igerant feed. to said cooling unit,responsive to two forces, one force being the pressure of therefrigerant fluid, in said cooling unit, and tending to increase thefeed with reducing pressure and vice versa, the other force beingresponsive to temperature conditions ot the refrigerant fluid passingthrough said o'utlet and tending to decrease the feed with

